1. Field of the Invention
This invention relates to an improvement in a developer reservoir joined to a developing device in an electrophotographic reproducing machine or an electrostatic recording apparatus, such as a laser printer and used to supplementarily supply a developer to the developing device.
2. Description of the Prior Art
In general, in an electrostatic recording apparatus, an electrostatic latent image on a turning image retainer is developed by a developing device, and a powdered toner in a developer is applied to the electrostatic latent image to develop the latent image into a toner image, which is then transferred and fixed to recording paper. Since the powdered toner is consumed as the development of the latent image progresses, it is necessary that the toner be supplementarily supplied to the developing device correspondingly to the consumption thereof. A developer make-up unit (developer hopper) is provided as a storage unit for the toner to be supplementarily supplied.
A large quantity of toner is contained in the developer make-up unit, and, before this toner has been completely consumed, toner is supplementarily supplied from a toner tank (developer reservoir) to the developer hopper.
The above is a description of a toner resupplying operation in an electrostatic recording apparatus using a dry two-component developer. The same developer resupplying operation is also required in an electrostatic recording apparatus using a one-component developer.
In both the case where a two-component developer is used and the case where a one-component developer is used, a developer resupplying operation is generally carried out by introducing a developer from the developer reservoir into the developer hopper.
The powdered developer is liable to fly off. During the developer resupplying operation, the developer flies off and floats, or flows and scatters from the openings of the developer reservoir and hopper to the outside to cause the outside air and the operator's clothes to be contaminated. Many means for preventing this inconvenience have been proposed.
These proposed means include a developer reservoir disclosed in Japanese Utility Model Laid Open No. 114572/1984. In this developer reservoir, a developer is held in a box type reservoir body, and a bottom opening of this reservoir body is sealed with a flexible film, one end of which is fixed to a movable cover. In order to resupply the developer, the movable cover is opened, so that the film is drawn to cause the bottom opening of the reservoir body being opened gradually, whereby the developer in the reservoir body falls from the opening into a hopper.
The developer placed in the hopper is supplementarily supplied at a suitable and constant rate from a supply port at a lower portion of the hopper to the interior of the developing device. In order to carry out the resupplying of the developer properly, this supply port is set to a length substantially equal to the total length of a developing sleeve and a photosensitive drum in the developing device.
Such a developer reservoir is joined to the front side of the developing device, and the developer falling from the developer reservoir has to be sent from the front side of the hopper thereinto by a rotary screw. This necessarily causes not only the construction of the interior of the hopper but also the construction of a means for placing the developer to a uniform height in the hopper to become complicated.
Especially, in a multicolor copier, in which a developing device is provided detachably so that the developing device can be replaced by a developing device containing a different developer, i.e. a different color toner, a power transmission means for connecting a rotary screw in a hopper and a driving power source in a copier body becomes complicated. It is demanded that, during a developer resupplying operation, the developer falls uniformly from a developer reservoir into a hopper, accordingly.